The present invention relates to a drilling machine for drilling large drilling holes in rock, especially to be used underground. More particularly, it relates to a drilling machine which is provided with a rotary drilling drive having a reducing transmission and drive motors longitudinally displaceable on supports.
A drilling machine of the above mentioned general type is disclosed, for example, in the German document DE-AS 2,114,651 and also in the U.S. Pat. No. 3,330,164. In both drilling machines their drive motors with pinions cooperate with a common transmission gear and can be turned on and turned off as hydraulic motors hydraulically and when needed mechanically, for example, by claw couplings. Thereby the torque transmitted to the common transmission gear and its number of revolutions can be varied. However, such a multi-motor drive for drilling machines of the above mentioned type can be used only to a limited extent, since the effect of the rotary speed limit is very limited for hydraulic motors in the idle running. The parallel circuit in FIG. 6 of the German document DE-AS 2,114,651 provides the action of the respective switched off hydraulic motor as a pump, and it must be provided with a free running, that is however not well known and at high rotary speed can lead to cavitation problems. The further proposed coupling mechanical elements are structurally and operationally expensive, therefore experts skilled in the art have been very restrained in carrying such expenses in practice. Since furthermore with such drives the total drive energy must be hydraulically transmitted, one or several space consuming, heavy and expensive hydraulic aggregates are required. Such a multi-motor drive therefore has no significant advantage in view of the required hydraulic station.
Transmission-amplification drilling devices will find further utilization, especially the device in accordance with the German reference DE-PS 3,445,492 designed for relatively lighter drilling machines. Its drive output must be however significantly increased, and thereby with the known drive art very large and expensive hydraulic stations as compared with the drilling machine are needed.